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  • Author or Editor: István Vetõ x
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A gömbhéjak horpadási alakját a kutatók jelentős része forgásszimmetrikusnak feltételezi. A megváltozott alak a gömbfelület egy részének egy sík által való lemetszésével, és a lemetszett résznek a síkra való tükrözésével nyerhető. Általában az a feltételezés, hogy az eredeti gömb és a tükrözött gömbrész csatlakozási vonala, a horpadási él kör alakú. Kevesen foglalkoznak az ettől eltérő, de a kísérletek során sokszor tapasztalt poligonális horpadási alakkal, melynél a horpadási él valamely szabályos sokszöghöz hasonlít. Az irodalomkutatás alapján az erre az esetre vonatkozó megállapításuk egységesen az, hogy a kérdés nem megoldott, a téma további vizsgálatot igényel. Kutatásunk célja a gömbhéj valódi horpadási alakjának meghatározása, továbbá a horpadást leíró teher-elmozdulás összefüggés meghatározása. Ehhez olyan kvalitatív modellt dolgoztunk ki, mely visszaadja a kísérletek során tapasztalható viselkedést. Bemutatjuk ezen kívül azt is, hogy a horpadási él poligonális alakja a rugalmasan ágyazott síkbeli nyomott gyűrű kihajlásával is összefüggésbe hozható. A cikkben az elméleti eredményeket kísérleti eredmények támasztják alá.

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The paper considers the buckling of complete spherical shells. The main purpose could be, as a basis for real design, to find the lower critical load. Three scientists developed the idea that the buckled shape of the shell is the isometrically transformed shape of the original shell surface. Applying this idea using rotationally symmetric buckled shape the lower critical load can be calculated fairly easily for spherical shells. In reality the buckled shape has rather discrete rotation symmetry. Considering this kind of buckled shape is the main task of our research. Some preliminary results related to this buckling form will be presented here.

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Numerous accumulations of CO2 and nitrogen-rich natural gas are known in the hot Pannonian Basin System (PBS), where even the mixture of these two fluids is a common phenomenon. The Danube Basin, part of the PBS, is characterized by the predominance of CO2 and nitrogen-rich natural gas over “normal” natural gas. The multistacked Répcelak and Mihályi gas accumulations (southern, Hungarian part of the Danube Basin) display an upward increase of nitrogen-rich natural gas at the expense of CO2. This study, using the abundant public data, the published results and the new biomarker data obtained from oil traces, attempts to explain the formation of these multistacked accumulations. A synoptic view of the vertical changes in gas composition, the maturation history of the basin and its basement, the chronology of the Neogene basaltic volcanism and the biomarker pattern of the oil traces resulted in the recognition of the metasedimentary origin of the nitrogen-rich natural gas and in a relative chronology of the mixing of the two gases and the oil.

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Central European Geology
Authors: József Fekete, Csanád Sajgó, István Horváth, Zoltán Kárpáti, István Vetõ and Magdolna Hetényi

Abstract

The geochemical facies of Hungarian thermal waters were the object of this study. Samples were separated into groups by relative ages (δ18O values). Mature and immature subgroups were formed on the basis of dissolved (semi)volatile organic compounds. The oldest (connate) waters form one group with a small number of samples. The subgroups containing different small molecular-sized soluble aromatics differ sharply in their chemical features (sodium, hydrogen carbonate, iodine, ammonium etc. content). The origin of the organic matter may differ in the subgroups as inferred by their different δ18O values and ten times greater halogen contents.

Our results show that the decomposition of organic matter produces small molecular-sized aromatic compounds and also influences the amounts of inorganic components in thermal waters, through the increase of feldspar hydrolysis and carbonate dissolution.

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Central European Geology
Authors: István Vető, Katalin Báldi, Stjepan Ćorić, Magdolna Hetényi, Attila Demény and István Futó

This study is intended to clarify the depositional environment of a 180-m-thick, immature, limy Middle Miocene oil source rock interval, cored in the Zala Basin, western Hungary. For this purpose, a highly interdisciplinary approach was applied combining simple, standard micropaleontological, isotopic, and organic geochemical methods, rarely applied together. Foraminifera were studied for estimating bottom oxygenation and water depth, while nannoplankton biostratigraphy permitted for estimating the rate of sedimentation. The studied source rocks were deposited in a rather shallow sea, below well-oxygenated bottom water. The abundant epiphytic foraminiferal fauna proves that the bottom was densely inhabited by benthic algae, while the high δ13Corg (>–22‰) clearly indicates massive benthic algal contribution to the kerogen. Mass accumulation rate of the limy upper part of the NN5 nannoplankton biozone, the oil source interval included, was very high (551 t/m2/Ma). In spite of moderate productivity and good oxygenation of the bottom, rapid accumulation of carbonate, produced partly by benthic algae, assured both the great relative weight of the marine organic components and their good preservation. Our results provide the first proof for the possibility of a major contribution of benthic algae to oil-prone kerogen.

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